The present invention relates to an apparatus and method for the treatment of gas streams containing organic and inorganic pollutants, suitable for applications such as treatment of streams resulting from fabrication of semiconductor materials and devices, micro-electric products, manufacturing of compact discs and other memory devices.
The gaseous effluents from the manufacturing of semiconductor materials, devices, products and memory articles involves a wide variety of chemical compounds used and produced in the process facility. They contain inorganic and organic compounds, breakdown products of photo-resist and other reagents, and a wide variety of other gases which must be removed from the waste gas streams before being vented from said facility. Typical to the industry, such effluents, either as a single component or multi-component composition, are mixed with an oxidant, such as high purity oxygen, air, nitrous oxide, or other reagents and thermally reacted and/or oxidized at elevated temperatures in a central reaction chamber.
In semiconductor manufacturing processes, various processing operations can produce combustible gas streams. Hydrogen and a variety of hydrides, VOC""s, PFC""s, HAP""s, etc. may be present and, if combined with air, oxygen or other oxidant species such as nitrous oxide, chlorine, fluorine and the like, form reactive mixtures.
However, the composition of the waste gas generated at a workstation may vary widely over time as the successive process steps are carried out. Additionally there are many different wafer process tools with many different recipe chemistries used in typical semiconductor process facilities.
With this variation of the composition of waste gas streams and the need to adequately treat the waste gas on a continuous basis during the operation of the facility, a common approach taken is to provide a single large-scale waste treatment system for an entire process facility. Such systems are almost always over-designed in terms of its treatment capacity, and typically do not have the ability to safely deal with a large number of mixed chemistry streams without posing complex reactive chemical risks. The operating cost associated with heating an extremely dilute mixed gas stream to appropriate elevated temperatures to achieve abatement performance targets is also an issue, in addition to the huge capital cost associated with large scale oxidation units, which often use catalytic chemistry. Furthermore, one of the problems of great concern in gas effluents is the formation of acid mist, acid vapors, acid gases and NOx (NO, NO2). The present invention provides a method for alleviating the formation of NOx by the appropriate injection of additives into the reactor which not only minimizes or eliminates, NOx formation, but also yield less acidic, hence less corrosive effluents.
The present invention provides compact, dedicated units, which may be employed at the point of use. They are designed to serve a single tool, or group of similar chemistry process tools, individual processing operation, or group of abatement compatible process operations to effectively and efficiently remove pollutants without being over-designed with respect to volume capacity, chemical complexity, heat generation and power consumption.
The present invention provides a process for abating chemical pollutants in a pollutant-containing gas stream by introducing the gas stream into a reactor chamber through a conduit, which accommodates at least one secondary inlet through which is introduced at least one gaseous reagent (with or without additional gaseous, liquid or solid reagents) to cause a controlled reaction in the gas stream by mixing and optionally, by heating. The desired reagent may also be generated in situ (e.g., thermally formed) in the mixing stream. Said reagent(s), added through inlets and/or directly or as precursor(s) into the reactor chamber, may be selected from the group consisting of hydrogen, hydrocarbons, ammonia, air, oxygen, water vapor, alcohol, ethers, calcium compounds, amines, and a mixture of these gases, liquids and/or solids. For example, mixtures such as ammonia/air and ammonia/oxygen have been found to be useful reagents. The reaction of the pollutant containing gas stream with the reagent is within the temperature range of about 650 C to 950 C.
The present invention provides an apparatus for removing pollutants from gaseous streams. It comprises a pre-reaction injection section, a thermal reactor section and a liquid scrubber section to achieve target abatement performance. In one embodiment, ports are located in the pre-reactor injection section and/or the main thermal reaction chamber for introducing a gas in such a way as to reduce or alleviate particle build-up in the main reactor section.
The thermal reactor is provided with at least one inlet comprising a conduit terminating with a portion of the conduit within the reactor which projects into the reactor into a tube defining an area in which there could be flame formation (hot zone or reaction zone).
The thermal reactor comprises a central chamber accommodating heating elements, a side inlet communicating with an exterior air space between the exterior wall and the heating elements, and an interior air space optionally communicating with the exterior air space. There is also, optionally, a distributor for introducing a gas, liquid and/or solid into the central chamber at a distance from the open end of the tube.
In one embodiment, the distributor is located out of the hot zone. The interior air space is defined by the interior wall and the heating elements, and an orifice means of introducing gas, liquid and/or solid into the central chamber through the interior wall, the inlet section, and/or the central chamber open end. The orifice may be located upstream of a hot zone created at the open end of the conduit and/or located downstream of the hot zone. The gases exiting the thermal reactor are cooled when passed through a liquid cooling section containing a vortex and/or spray chamber.
The cooled gases from the combustion chamber are then passed through a counter-current and/or co-current flow packed bed liquid scrubber for chemical pollutant scrubbing and trapping and condensing particles by flowing the gas stream through the packed bed with or against a flowing liquid. Inlets are provided for introducing gases to the upper portion of the bed to lower the exhaust dew point.
The present invention also, optionally, has a means of sensing gases, liquids and/or solids for the purpose of monitoring and/or controlling the invention at desired and/or optimal operating conditions.